Prussian blue composite material and preparation method and application thereof

Abstract

This invention relates to a Prussian blue composite material, its preparation method, and its applications. First, carbon cloth is heated and ultrasonically cleaned to remove the hydrophobic coating, oily substances, and impurities from its surface. Then, the pretreated carbon is placed in a cerium salt-urea mixed solution for a hydrothermal reaction to obtain cerium hydroxide-coated carbon cloth. The cerium hydroxide-coated carbon is then placed in a tube furnace and heat-treated at 300-600°C in air for approximately 1 hour for later use. A cobalt salt-citrate mixed solution and a potassium ferricyanide solution of a certain concentration are prepared separately. The carbon obtained in the previous step is placed in the potassium ferricyanide solution, and then the cobalt salt-citrate mixed solution is slowly added dropwise through a separatory funnel. After the addition is complete, the immersion reaction is carried out for 24 hours to obtain the Prussian blue composite material. This Prussian blue composite material exhibits excellent performance in the hydrogen and oxygen evolution reactions of water electrolysis, not only reducing the energy consumption of water electrolysis but also significantly improving the hydrogen production efficiency, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to a Prussian blue composite material, its preparation method, and its application. Background Technology

[0002] With the continuous rise in global energy demand, hydrogen energy, as a clean and sustainable energy source, has great development potential. There are multiple methods for producing hydrogen, among which hydrogen evolution by electrolysis (HER) has attracted widespread attention due to its large-scale application and high purity of the produced hydrogen. Platinum is currently the most efficient HER electrocatalyst, but its poor stability and high price significantly limit its widespread commercial application. Therefore, developing a low-cost, high-performance, and stable electrocatalyst material for use in HER is extremely urgent.

[0003] Prussian blue materials are porous, which facilitates the adsorption of small molecules. Furthermore, their good stability makes them an excellent choice as catalysts for water electrolysis. In recent years, cerium oxide, as a transition metal oxide, has gained attention due to its abundant oxygen vacancy defects and Ce content. 3+ and Ce 4+ Its flexible transformation between states makes it a hot material in the field of catalysis.

[0004] This invention combines the advantages of Prussian blue and cerium, and uses a relatively simple hydrothermal method and solution immersion method to prepare a Prussian blue composite catalyst. While optimizing material performance, it improves raw material utilization, reduces production energy consumption, and simplifies the process, making it suitable for large-scale industrial production. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for preparing Prussian blue composite material, which mainly includes the following steps: (a) adding pretreated carbon cloth to a mixed solution containing cerium salt and urea for hydrothermal reaction to obtain carbon cloth coated with cerium hydroxide; (b) heat-treating the carbon cloth coated with cerium hydroxide, and then reacting it with potassium ferricyanide, cobalt salt and citrate in solution.

[0006] Furthermore, the pretreatment of the carbon cloth in step (a) includes heating and ultrasonic cleaning. Heating is mainly to remove the hydrophobic coating and oily substances on the surface of the carbon cloth, while ultrasonic cleaning is mainly to remove residual impurities on the surface of the carbon cloth, thereby ensuring the coating effect and product performance.

[0007] Furthermore, the heating process is as follows: the carbon cloth is placed in a tube furnace, heated to 600-700℃ in an air atmosphere and held for 30-60 minutes, then naturally cooled to room temperature. The ultrasonic cleaning process is as follows: the heat-treated carbon cloth is added to deionized water for ultrasonic cleaning and then removed.

[0008] Furthermore, the cerium salt is selected from at least one of cerium nitrate, cerium ammonium nitrate, cerium chloride, and cerium oxalate; the cobalt salt is specifically at least one of cobalt nitrate, cobalt nitrate, cobalt acetate, cobalt carbonate, and cobalt sulfate; and the citrate is specifically sodium citrate or potassium citrate.

[0009] Furthermore, the concentration of cerium salt in the mixed solution described in step (a) is 0.03-0.1 mol / L, and the molar ratio of cerium salt to urea is 1:1-30.

[0010] Furthermore, in step (a), the hydrothermal reaction temperature is 120-160℃ and the hydrothermal reaction time is 6-12 hours.

[0011] Furthermore, in step (b), the heat treatment temperature is 300-600℃, the heat treatment time is 1-3 hours, and the heat treatment atmosphere is air.

[0012] Further, step (b) is as follows: the heat-treated carbon cloth is added to a potassium ferricyanide solution, and then a cobalt salt-citrate mixed solution is added dropwise to react.

[0013] Furthermore, the concentration of the potassium ferricyanide solution is 0.01-0.2 mol / L, and the total concentration of the cobalt salt-citrate mixed solution is 0.05-0.5 mol / L, wherein the molar ratio of cobalt salt to citrate is 1:1-5.

[0014] Furthermore, the volume ratio of potassium ferricyanide solution to cobalt salt-citrate mixed solution is 1:1-3.

[0015] Furthermore, the dropping rate of the cobalt salt-citrate mixed solution was kept constant, and stirring was performed simultaneously. After the addition was completed, the mixture was allowed to stand for more than 24 hours before the product was removed and dried. This dropping method can slow down the reaction rate and reduce the particle size of the Prussian blue precipitate. The long standing time after the addition is beneficial to the nucleation and growth of Prussian blue crystals.

[0016] The second objective of this invention is to provide a Prussian blue composite material prepared according to the above method.

[0017] The third objective of this invention is to provide the application of the above-mentioned Prussian blue composite material in the electrolysis of water for hydrogen and oxygen evolution.

[0018] This invention relates to a multi-step reaction: (1) First, cerium salt is reacted with urea to obtain cerium hydroxide particles uniformly grown on conductive carbon cloth, and then cerium dioxide is obtained by high-temperature annealing in air. Cerium dioxide can be used as an auxiliary agent for oxygen evolution reaction; (2) Cobalt ions are complexed with ferricyanide by solution method to obtain cobalt iron Prussian blue material K2CoFe(CN)6, wherein sodium citrate can control the particle size of Prussian blue particles; (3) Finally, the carbon cloth coated with cerium dioxide obtained in the previous step is immersed in a mixed solution to obtain Prussian blue composite material.

[0019] The beneficial effects of this invention are mainly reflected in the following aspects: (1) It integrates the advantages of Prussian blue and cerium, achieving a strong combination, and uses a simple hydrothermal method and solution soaking method to prepare a high-performance Prussian blue composite catalyst; (2) The product obtained exhibits excellent performance in the hydrogen evolution and oxygen evolution reactions of water electrolysis, which not only reduces the energy consumption of water electrolysis, but also greatly improves the hydrogen production efficiency of water electrolysis; (3) The process of this invention is simple and easy to implement. While optimizing the material performance, it improves the utilization rate of raw materials, reduces production energy consumption, simplifies the process flow, and is suitable for large-scale industrial production. Attached Figure Description

[0020] Figure 1 X-ray diffraction pattern of the Prussian blue composite material prepared in Example 1;

[0021] Figure 2 The graph shows the HER performance of the Prussian blue composite material prepared in Example 1 in a 1.0 M KOH solution.

[0022] Figure 3 The graph shows the OER performance of the Prussian blue composite material prepared in Example 1 in a 1.0 M KOH solution. Detailed Implementation

[0023] To enable those skilled in the art to fully understand the technical solution and beneficial effects of the present invention, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0024] Example 1

[0025] (1) Arrange the carbon in a tube furnace, heat it to 600°C in an air atmosphere and keep it at that temperature for 30 minutes. After cooling it to room temperature, add deionized water and ultrasonically clean it for 30 minutes. Then take it out for use.

[0026] (2) Add 0.001 mol cerium nitrate and 0.03 mol urea to 30 mL of deionized water and stir for 30 min to obtain a cerium nitrate-urea mixed solution. Place the treated carbon cloth into the cerium nitrate-urea mixed solution and heat to 160 °C for hydrothermal reaction for 8 h. During this period, cerium hydroxide grows on the carbon cloth to complete the coating. Wash the cerium hydroxide-coated carbon cloth 2-3 times with deionized water and anhydrous ethanol, and then dry it in a 60 °C forced-air drying oven for later use.

[0027] 3) The carbon cloth coated with cerium hydroxide was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in air atmosphere and held for 1 hour to obtain carbon cloth coated with cerium oxide.

[0028] 4) Dissolve 0.005 mol cobalt nitrate and 0.005 mol sodium citrate in 100 mL of deionized water to obtain mixed solution A. Dissolve 0.005 mol potassium ferricyanide in 100 mL of deionized water to obtain solution B. Place the carbon cloth obtained in step (3) into solution B. Slowly add mixed solution A to solution B at a constant rate using a separatory funnel. After the carbon cloth is soaked and reacted in the mixed solution for 24 hours, Prussian blue composite material is obtained.

[0029] The XRD pattern of the Prussian blue composite material prepared in Example 1 is shown below. Figure 1 As shown. After comparison with the standard PDF card library, it was found that the sample material in Example 1 corresponds one-to-one with the standard card PDF#31-1000 for K2CoFe(CN)6 and the standard card PDF#44-1001 for cerium dioxide, proving that the Prussian composite material was successfully synthesized.

[0030] The HER performance of the Prussian blue composite material prepared in Example 1 in 1.0 M KOH solution was tested. The test conditions were as follows: a three-electrode electrochemical system, a Shanghai Chenhua Chi660e electrochemical workstation, a saturated calomel electrode as the reference electrode, a carbon rod as the counter electrode, and the Prussian blue composite material fixed with platinum clips as the working electrode. The sample size was 0.6 cm × 0.8 cm. The test potential range was -1 V to -1.5 V, and the scan rate was 5 mV / s. The test results are as follows. Figure 2 As shown in the figure, this Prussian blue composite material exhibits good hydrogen evolution performance. At a current density of 10 mA·cm⁻¹, -2 At that time, the overpotential was only 0.15V.

[0031] The OER performance of the Prussian blue composite material prepared in Example 1 in 1.0 M KOH solution was tested. The test conditions were as follows: a three-electrode electrochemical system, a Shanghai Chenhua Chi660e electrochemical workstation, a saturated calomel electrode as the reference electrode, a carbon rod as the counter electrode, and the Prussian blue composite material fixed with platinum clips as the working electrode. The sample size was 0.6 cm × 0.8 cm. The test potential range was -0.05 V to 0.95 V, and the scan rate was 5 mV / s. The test results are as follows. Figure 3 As shown. By Figure 3 It can be seen that this Prussian blue composite material has good oxygen evolution properties. At a current density of 50 mA·cm⁻¹ -2 At that time, the overpotential required is only 0.39V.

[0032] Example 2

[0033] (1) Arrange the carbon in a tube furnace, heat it to 600°C in an air atmosphere and keep it at that temperature for 30 minutes. After cooling it to room temperature, add it to deionized water and ultrasonically clean it for 30 minutes. Then take it out for use.

[0034] (2) Add 0.003 mol cerium nitrate and 0.03 mol urea to 30 mL of deionized water and stir for 30 min to obtain a cerium nitrate-urea mixed solution. Place the treated carbon cloth into the cerium nitrate-urea mixed solution and heat to 140 °C for hydrothermal reaction for 10 h. During this period, cerium hydroxide grows on the carbon cloth to complete the coating. Wash the cerium hydroxide-coated carbon cloth with deionized water and anhydrous ethanol 2-3 times in sequence, and then dry it in a 60 °C forced-air drying oven for later use.

[0035] 3) The carbon cloth coated with cerium hydroxide was placed in a tube furnace and heated to 450°C at a heating rate of 5°C / min in air atmosphere and held for 1 hour to obtain carbon cloth coated with cerium oxide.

[0036] 4) Dissolve 0.002 mol cobalt nitrate and 0.006 mol sodium citrate in 100 mL of deionized water to obtain mixed solution A. Dissolve 0.002 mol potassium ferricyanide in 100 mL of deionized water to obtain solution B. Place the carbon cloth obtained in step (3) into solution B. Slowly add mixed solution A to solution B at a constant rate using a separatory funnel. After the carbon cloth is soaked and reacted in the mixed solution for 36 hours, Prussian blue composite material is obtained.

[0037] Example 3

[0038] (1) Arrange the carbon in a tube furnace, heat it to 600°C in an air atmosphere and keep it at that temperature for 30 minutes. After cooling it to room temperature, add it to deionized water and ultrasonically clean it for 30 minutes. Then take it out for use.

[0039] (2) Add 0.005 mol cerium nitrate and 0.09 mol urea to 30 mL of deionized water and stir for 30 min to obtain a cerium nitrate-urea mixed solution. Place the treated carbon cloth into the cerium nitrate-urea mixed solution and heat to 120 °C for hydrothermal reaction for 12 h. During this period, cerium hydroxide grows on the carbon cloth to complete the coating. Wash the cerium hydroxide-coated carbon cloth 2-3 times with deionized water and anhydrous ethanol, and then dry it in a 60 °C forced-air drying oven for later use.

[0040] 3) The carbon cloth coated with cerium hydroxide was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in air atmosphere and held for 1 hour to obtain carbon cloth coated with cerium oxide.

[0041] 4) Dissolve 0.008 mol cobalt nitrate and 0.02 mol potassium citrate in 100 mL of deionized water to obtain mixed solution A. Dissolve 0.008 mol potassium ferricyanide in 100 mL of deionized water to obtain solution B. Place the carbon cloth obtained in step (3) into solution B, and add mixed solution A dropwise into solution B at a constant rate through a separatory funnel. After the carbon cloth is soaked in the mixed solution for 24 hours, the Prussian blue composite material is obtained.

Claims

1. A method for preparing a Prussian blue composite material, characterized in that, The method includes the following steps: (a) adding pretreated carbon cloth to a mixed solution containing cerium salt and urea for hydrothermal reaction to obtain carbon cloth coated with cerium hydroxide; (b) heat-treating the carbon cloth coated with cerium hydroxide, and then reacting it with potassium ferricyanide, cobalt salt, and citrate in a solution. The specific process is as follows: the heat-treated carbon cloth is added to a potassium ferricyanide solution, and then a cobalt salt-citrate mixed solution is added dropwise for reaction. The dropwise addition rate of the cobalt salt-citrate mixed solution is kept constant and stirred while adding. After the addition is completed, the product is taken out and dried after standing for more than 24 hours.

2. The method as described in claim 1, characterized in that: The pretreatment of carbon cloth in step (a) includes heating and ultrasonic cleaning. The heating process is as follows: the carbon cloth is placed in a tube furnace, heated to 600-700℃ in an air atmosphere and kept at that temperature for 30-60 minutes, and then naturally cooled to room temperature. The ultrasonic cleaning process is as follows: the heated carbon cloth is added to deionized water for ultrasonic cleaning and then taken out.

3. The method as described in claim 1, characterized in that: The cerium salt is selected from at least one of cerium nitrate, cerium ammonium nitrate, cerium chloride, and cerium oxalate; the cobalt salt is selected from at least one of cobalt nitrate, cobalt acetate, cobalt carbonate, and cobalt sulfate; and the citrate is specifically sodium citrate or potassium citrate.

4. The method as described in claim 1, characterized in that: The concentration of cerium salt in the mixed solution in step (a) is 0.03-0.1 mol / L, the molar ratio of cerium salt to urea is 1:1-30, the hydrothermal reaction temperature is 120-160℃, and the hydrothermal reaction time is 6-12 hours.

5. The method as described in claim 1, characterized in that: In step (b), the heat treatment temperature is 300-600℃, the heat treatment time is 1-3 hours, and the heat treatment atmosphere is air.

6. The method as described in claim 1, characterized in that: The concentration of potassium ferricyanide solution is 0.01-0.2 mol / L, and the total concentration of cobalt salt-citrate mixed solution is 0.05-0.5 mol / L, wherein the molar ratio of cobalt salt to citrate is 1:1-5.

7. The method as described in claim 1, characterized in that: The volume ratio of potassium ferricyanide solution to cobalt salt-citrate mixed solution is 1:1-3.

8. A Prussian blue composite material, characterized in that: The material is prepared according to any one of claims 1-7.

9. The application of the Prussian blue composite material of claim 8 in the electrolysis of water for hydrogen and oxygen evolution.

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